Device for accomodating electronic components

ABSTRACT

A device for accomodating at least one, preferably electrical or electronic, component, comprising a housing forming an interior defined by an inner wall surface, in which interior the at least one component is arranged, the at least one component occupying less than all of the interior of the housing, the balance being filled with a casting material, wherein a projection from the inner wall surface encircles the interior and forms an undercut filled by the casting material to lock the casting material to the inner wall surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application filed under 35U.S.C. §371, claiming priority of International Application No.PCT/EP01/01666, filed Feb. 15, 2001 in the European Patent Office, andDE 100 08 695.0, filed Feb. 24, 2000 in the German Patent Office, under35 U.S.C. §§119 and 365.

BACKGROUND OF THE INVENTION

The invention relates to a device for accommodating at leastone—preferably electrical or electronic—component, comprising a housing,in the interior of which the at least one component is arranged, theinterior of the housing being filled with a casting material.

It is known to use hot-melt adhesives for the production of mouldedparts or for the sealing of plug connectors or as an encapsulating massfor electrical or electronic components. Thus, hot-melt adhesives havebeen employed, for example, for years for water-tight plug connectors.In addition, there are also special hot-melt adhesives on a polyamidebase (for example, the product Macromelt (Registered Trade Mark)marketed by the applicant) which provide more than just a water-tightadhesion. Such an adhesive prevents, in particular, not only the ingressof moisture into the plug, but also imparts mechanical strength to theplug connector and fulfills further tasks which were previouslyfulfilled by additional, high-cost plastic parts. Hot-melt adhesives ofthis kind are based on, for example, polyamide and have a melt rangefrom 120 to 180° C. They adhere to many plastics, such as polyethylene,polyvinylchloride and polyamide, and have low viscosity. In one methodused for injection moulding, the heated hot-melt adhesive is injectedinto a tool. The liquid melt is suitable for flowing around filigreecomponents, even without high pressure, without impairing the functionof the components. The adhesive penetrates into the smallest spaces evenat a pressure between 5 and 10 bars. The low pressure has theconsequence that the entire method is very economic, since the machinecan be designed for this low loading. The tools can be producedfavourably in cost from aluminium. This method is suitable for, forexample, encapsulating cable passages or for wire insulation. Theencapsulation of switches, plugs, contacts, sensors and other electroniccomponents is equally possible and opens up a further field of use. Sucha method can be used wherever electrical currents flow and sealing isnecessary.

In principle it is possible to either fill a housing, in which theelectronic component is arranged, with cast hot-melt adhesive or toproduce the entire housing itself from hot-melt adhesive. However, sucha housing consisting solely of hot-melt adhesive has only a lowmechanical strength compared with a plastic material housing andaccordingly can be used only in specific applications.

In the case of use of devices according to category with a plasticmaterial housing and an internal filling of casting material consistingof hot-melt adhesive the problem arises, however, that under temperaturechange of the finished units the hot-melt adhesive detaches again fromthe housing wall so that the electronic component or components in thehousing is or are no longer sealed. For this reason it has been usual inthe past to injection-mould hot-melt adhesive completely externallyaround the housing. However, due to space considerations this is notalways possible.

It is therefore the object of the invention to further develop a deviceaccording to category, with maintenance of the mechanical strengththereof, so that it is reliably sealed towards the outside even in thecase of temperature changes.

DESCRIPTION OF THE INVENTION

According to the invention this object is met by a device of the kindstated in the introduction in the manner that the housing is provided atthe inner side with at least one encircling projection having anundercut.

When filling the housing, which is furnished with at least oneelectronic component or the like, with casting material the castingmaterial then also flows into the region between the housing inner walland the encircling projection and is thereby, so to speak, self-lockedto the housing. Even in the case of temperature change tests, i.e.extreme temperature changes, it is ensured that the casting materialcannot detach from the housing inner wall, so that the device as a wholeremains reliably sealed.

In that case it is then preferably provided that the projection isarranged in the centre region of the housing, so that the casting massis then retained approximately symmetrically in the housing.

As known per se, the casting material can with particular advantageconsist of hot-melt adhesive on a polyamide base. Preferably there canthen be used an adhesive placed on the market by the applicant under thedesignation Macromelt (Registered Trade Mark). Alternatively, otherhot-melt adhesives, for example on a polyurethane or polyester base, canalso be advantageously used.

If the housing is to be injection-filled with the casting material thehousing advantageously has at least one injection bore for the castingmaterial in the region of the projection. The injection bore thenpenetrates the projection which, however, is otherwise formed to beencircling.

The projection is Connected with the outer wall of the housing in rigidmanner it the projection encircles continuously and is connected withthe outer wall of the housing by means of a strut- or bridge-likeconnecting wall. In that case, it is preferably farther provided thatthe projection and connecting wall are together formed to becross-sectionally T-shaped.

In a particularly preferred development the invention further providesthat the projection encircles in sections and is connected with theouter wall of the housing by means of a respective connecting wall foreach section. This enables particularly good flowing of the bondingmaterial into the gap between the projection and the outer wall andprevents bubble formation in the region behind the undercutting of theprojection. In addition, this enables production of the housing of thedevice according to the invention in a plastic injection mouldingprocess with uniform wall thicknesses without the risk of shrink holesin the internal surface of the housing.

Finally, as also provided by the invention it is of particular advantagein the case of this embodiment if the connecting wall is formed to becircular in each section.

DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following, by way ofexample, with reference to the drawing, in which:

FIG. 1 shows a cross-section of a device according to the invention,

FIG. 2 shows the device according to FIG. 1, with emphasis of the sealedinternal region,

FIG. 3 shows a cross-section through a modified embodiment,

FIG. 4 shows a side view of the embodiment according to FIG. 2,

FIG. 5 shows a cross-section through a third embodiment,

FIG. 6 shows a plan view of the embodiment according to FIG. 5 and

FIG. 7 shows a side view of the embodiment according to FIGS. 5 and 6.

In the following the same or analogous elements or component parts ofthe various embodiments are provided in each instance with the samereference numerals.

A device according to the invention is denoted generally by 1 in FIG. 1.This device 1 comprises, in this embodiment, a tubular housing 2, forexample of plastic, and serves for sealed accommodation of aschematically illustrated electronic component 8. After arrangement ofthis electronic component 8 in the housing 2, the housing 2 is filledout in the interior with a casting material 3, preferably a hot-meltadhesive on a polyamide base. This can be, for example, the adhesiveknown as Macromelt (Registered Trade Mark).

In order to ensure that the interior of the housing 2 remains sealedeven in the case of temperature fluctuations or, in particular, in thecase of temperature change tests, the housing 2 is provided at the innerside with at least one encircling projection 4 having an undercut. Thisprojection 4 is preferably formed—as in the first two embodiments—to beT-shaped and is preferably arranged in the centre region of the housing2. The projection 4 is fixedly connected with the outer wall 10 of thehousing 2 by way of a web-shaped connecting wall 9 similarly formed tobe encircling, the connection preferably being produced integrally bymeans of a plastic injection-moulding process.

By virtue of this design, casting material introduced in liquid stateoptionally under slightly increased pressure flows in the device 1 alsointo the spaces 5 between the projection 4 and the inner wall surface ofthe housing 2. The casting material 3 hardens here as well, so that thecasting material 3 is, so to speak, locked in these spaces 5. If thehousing 2 and the casting material 3 now expand differently in the caseof temperature changes, it is nevertheless ensured, since the castingmaterial is fixed by the locking in the spaces 5, that the device 5remains sealed to the outside. This sealed region is indicated in FIG. 2by a rectangle 6, and in the region of this rectangle 6 there isavailable a reliably sealed region within the device 1 in whichelectronic components can be arranged to be securely sealed byencapsulation with hot-melt adhesive.

A further embodiment of a device according to the invention isillustrated in FIGS. 3 and 4. The device again denoted by 1 here has ahousing 2 of different form. As in the case of the embodiment accordingto FIGS. 1 and 2, the housing 2 is provided at the inner side with anencircling, T-shaped projection 4. In order to enable injection of thecasting material in the case of a housing 2 formed in that manner, thehousing 2 has at least one injection bore 7 for the casting material 3in the region of the projection 4. Apart from this injection bore 7, theprojection 4 is, however, otherwise formed to be encircling so as toensure the sealing function.

In the case of the embodiment, which is illustrated without a castingmaterial filling and without an electronic component, according to FIGS.5 to 7 the connecting wall 11 connecting the encircling projection 4with the outer wall 10 is constructed only in sections and as an annularor circular connecting wall 11. In total the device 1 in the embodimentaccording to FIGS. 5 to 7 has four sections each with a respectivecircularly arranged connecting wall 11. Considered from the outer side,four bowl-like depressions 12 are formed in these sections in the outerwall 10 of the housing 2. It is also possible, however, to form theseregions to have a complete surface and thus design the outer surface ofthe housing 2 to be smooth or free of depressions. Since the connectionwall 11 is formed to encircle only in sections and no longercontinuously as in the embodiments according to FIGS. 1 to 4, thereresults at the regions of the connecting walls 11 a substantially open,encircling gap 13 between the inner side of the encircling wall 10 andthe encircling projection 4 of the housing 2, which is open outside theannular wall regions 11 also in the direction of viewing of the planview according to FIG. 7. In the case of the embodiments according toFIGS. 1 to 4 the connecting wall 9 is thereagainst formed with aparallel course continuously between the projection 4 and outer wall 10,so that in the direction of viewing of the side view according to FIG. 4the gap-like spaces 5 are separated from one another by means of theconnecting wall 9 and thus formed to be closed. In these embodiments,when the casting material 3 is cast the direct throughflow thereofwithin this gap-like opening from the space 5 of one side to the space 5of the other side is not possible. Thereagainst when the castingmaterial 3 is cast in the device 1 of the embodiment according to FIGS.5 to 7 this now flows substantially unhindered into the gap 13 (now nolonger separated by a partition wall into two spaces) and engages behindthe projection 4. Air disposed in the gap 13 can escape freely andwithout hindrance during inflow of the casting material without beinginstructed by a connecting wall of the projection 4 to the outer wall10. The risk of included air bubbles thus no longer exists.

The invention is obviously not restricted to the illustratedembodiments. Further embodiments are possible without departing from thebasic concepts. Thus, in the case of larger housings 2 severalprojections 4 can be provided in succession in direction towards thecentre of the device 1. In addition, the number of circular connectingwalls 11 can be adapted to the respective purpose of use of the device1. The connecting wall 11 can obviously also have any other desiredgeometric course, but can, in particular, also be constructed as acomplete cylinder and thus as a rod-shaped connection between the outerwall 10 and projection 4.

What is claimed is:
 1. A device for accommodating at least oneelectrical or electronic component, comprising a housing forming aninterior defined by an inner wall surface, in which interior the atleast one component is arranged, the at least one component occupyingless than all of the interior of the housing, the balance being filledwith a casting material, wherein a projection from the inner wallsurface encircles the interior and forms an undercut filled by thecasting material to lock the casting material to the inner wall surface,wherein the projection continuously encircles the interior and isconnected with the housing wall by a strut- or bridge-like connectingwall, and wherein the projection and connecting wall together form across-sectional T-shape.
 2. The device of claim 1, wherein theprojection is arranged in a center region of the housing.
 3. The deviceof claim 2, wherein the casting material comprises polyamide-basedhot-melt adhesive.
 4. The device of claim 2, wherein the housing has inproximity to the projection at least one injection bore for the castingmaterial.
 5. The device of claim 1, wherein the casting materialcomprises polyamide-based hot-melt adhesive.
 6. The device of claim 1,wherein the housing has in proximity to the projection at least oneinjection bore for the casting material.
 7. A device for accommodatingat least one electrical or electronic component, comprising a housingforming an interior defined by an inner wall surface, in which interiorthe at least one component is arranged, the at least one componentoccupying less than all, of the interior of the housing, the balancebeing tilled with a casting material, wherein a projection from theinner wall surface encircles the interior and forms an undercut filledby the casting material to lock the casting material to the inner wallsurface, wherein the projection encircles the interior in sections, eachsection being connected to the housing wall by a respective connectingwall, and where in in the connecting walls are formed as cylindricalpedestals.
 8. The device of claim 7, wherein the projection is arrangedin a center region of the housing.
 9. The device of claim 8, wherein thecasting material comprises polyamide-based hot-melt adhesive.
 10. Thedevice of claim 8, wherein the housing has in proximity to theprojection at least one injection bore for the casting material.
 11. Thedevice of claim 7, wherein the casting material, comprisespolyamide-based hot-melt adhesive.
 12. The device of claim 7, whereinthe housing has in proximity to the projection at least one injectionbore for the casting material.
 13. A device for accommodating at leastone component, comprising a housing forming an interior defined by aninner wall surface, in which interior the at least one component isarranged, the at least one component occupying less than all of theinterior of the housing, the balance being filled with a castingmaterial comprising a hot-melt adhesive, wherein a projection from theinner wall surface encircles the interior and forms an undercut filledby the casting material to lock the casting material to the inner wallsurface.
 14. The device of claim 13, wherein the projection is arrangedin a center region of the housing.
 15. The device of claim 14, whereinthe housing has in proximity to the projection at least one injectionbore for the casting material.
 16. The device of claim 13, wherein thecasting material comprises polyamide-based hot-melt adhesive.
 17. Thedevice of claim 16, wherein the casting material comprisespolyamide-based hot-melt adhesive.
 18. The device of claim 13, whereinthe housing has in proximity to the projection at least one injectionbore for the casting material.
 19. The device of claim 13, wherein theprojection continuously encircles the interior and is connected with thehousing wall by a strut- or bridge-like connecting wall.
 20. The deviceof claim 19, wherein the projection and connecting wall together form across-sectional T-shape.
 21. The device of claim 13, wherein theprojection encircles the interior in sections, each section beingconnected to the housing wall by a respective connecting wall.
 22. Thedevice of claim 21, wherein in the connecting walls are formed ascylindrical, pedestals.